U.S. patent application number 17/592455 was filed with the patent office on 2022-08-25 for electrode plate and manufacturing method for electrode plate.
The applicant listed for this patent is Prime Planet Energy & Solutions, Inc., TOYOTA JIDOSHA KABUSHIKI KAISHA. Invention is credited to Miyuki MATSUYAMA, Momoka MIYAJIMA, Sokichi OKUBO, Nagisa SHIMASAKI, Tomoyuki UEZONO, Masaki WATANABE.
Application Number | 20220271270 17/592455 |
Document ID | / |
Family ID | |
Filed Date | 2022-08-25 |
United States Patent
Application |
20220271270 |
Kind Code |
A1 |
OKUBO; Sokichi ; et
al. |
August 25, 2022 |
ELECTRODE PLATE AND MANUFACTURING METHOD FOR ELECTRODE PLATE
Abstract
A manufacturing method for an electrode plate and an electrode
plate are provided. The method includes deposition-layer forming to
form a deposition layer in which active material particles and
binder particles are deposited on a surface of a current collecting
foil and heat pressing to form an electrode layer on the surface of
the current collecting foil by heating and compressing a
deposition-layer-formed current collecting foil having the
deposition layer on the surface of the current collecting foil. The
deposition layer includes a first deposition layer placed on a side
of the current collecting foil and a second deposition layer
constituting a surface of the deposition layer. The
deposition-layer forming includes forming the deposition layer in
which a content rate of the binder particles in the second
deposition layer is lower than a content rate of the binder
particles in the first deposition layer.
Inventors: |
OKUBO; Sokichi;
(Okazaki-shi, JP) ; UEZONO; Tomoyuki;
(Okazaki-shi, JP) ; MIYAJIMA; Momoka; (Toyota-shi,
JP) ; SHIMASAKI; Nagisa; (Nagoya-shi, JP) ;
WATANABE; Masaki; (Seto-shi, JP) ; MATSUYAMA;
Miyuki; (Toyota-shi, JP) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Prime Planet Energy & Solutions, Inc.
TOYOTA JIDOSHA KABUSHIKI KAISHA |
Tokyo
Aichi-ken |
|
JP
JP |
|
|
Appl. No.: |
17/592455 |
Filed: |
February 3, 2022 |
International
Class: |
H01M 4/139 20060101
H01M004/139; H01M 4/04 20060101 H01M004/04; H01M 4/36 20060101
H01M004/36; H01M 10/0525 20060101 H01M010/0525 |
Foreign Application Data
Date |
Code |
Application Number |
Feb 24, 2021 |
JP |
2021-027510 |
Claims
1. A manufacturing method for an electrode plate including an
electrode layer on a surface of a current collecting foil, the
method comprising: deposition-layer forming of forming a deposition
layer, in which a plurality of active material particles and a
plurality of binder particles are deposited and no solvent is
included, on the surface of the current collecting foil; and heat
pressing of forming the electrode layer on the surface of the
current collecting foil by heating and compressing a
deposition-layer-formed current collecting foil, in which the
deposition layer exists on the surface of the current collecting
foil, by use of a pair of heat press portions of a heat pressing
device, wherein the deposition layer includes a first deposition
layer placed on a side of the current collecting foil and a second
deposition layer constituting a surface of the deposition layer,
the deposition layer is formed in the deposition-layer forming such
that a content rate of the binder particles in the second
deposition layer is lower than the content rate of the binder
particles in the first deposition layer.
2. The manufacturing method for the electrode plate according to
claim 1, wherein the deposition-layer forming includes: forming the
first deposition layer formed of first composite particles in which
the binder particles having smaller diameter than the active
material particles are bound to surfaces of the active material
particles and no solvent is included; forming the second deposition
layer formed of at least any one of the active material particles
and second composite particles in which less binder particles than
those included in the first composite particles are bound to the
surfaces of the active material particles and no solvent is
included.
3. An electrode plate comprising: a current collecting foil; and an
electrode layer provided with a plurality of active material
particles and a plurality of binder particles and formed on a
surface of the current collecting foil, wherein the electrode layer
includes a first electrode layer placed on a side of the current
collecting foil and a second electrode layer constituting a surface
of the electrode layer, and a content rate of the binder particles
in the second electrode layer is lower than the content rate of the
binder particles in the first electrode layer.
4. The electrode plate according to claim 3, wherein the electrode
layer is formed such that the active material particles are bound
by the binder particles having smaller diameters than those of the
active material particles, and the number of the binder particles
existing around the active material particles included in the
second electrode layer is less than the number of the binder
particles existing around the active material particles included in
the first electrode layer.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application is based upon and claims the benefit of
priority from the prior Japanese Patent Application No. 2021-027510
filed on Feb. 24, 2021, the entire contents of which are
incorporated herein by reference.
BACKGROUND
Technical Field
[0002] The present disclosure relates to an electrode plate and a
manufacturing method for the electrode plate.
Related Art
[0003] Heretofore, as an electrode plate, an electrode plate
including an electrode layer formed on a surface of a current
collecting foil has been known. A manufacturing method for this
type of the electrode plate has been known as a technique disclosed
in JP2020-068113A, for example.
[0004] Firstly, in a deposition-layer forming process, a deposition
layer, in which active material particles and binder particles are
deposited on a surface of a current collecting foil and no solvent
is included, is formed. Specifically, there is prepared an
apparatus provided with a roller A and a roller B rotating to face
each other and configured such that the current collecting foil is
conveyed by the roller B by passing through a gap between the
roller A and the roller B to dispose a mixed powder body, in which
the electrode active material particles and the binder particles
are mixed and no solvent is included, on the surface of the current
collecting foil. To be in more detail, the mixed powder body is
serially supplied to an outer circumferential surface of the roller
A in a state that an electric potential difference is generated
between the roller A and the current collecting foil conveyed by
the roller B, and then there is further generated the electric
potential difference between the current collecting foil and the
mixed powder body supplied to the outer circumferential surface of
the roller A. Owing to the thus generated electric potential
difference, the mixed powder body is moved from the outer
circumferential surface of the roller A to a surface of the current
collecting foil by an electrostatic force exerted between the mixed
powder body and the current colleting foil, thereby serially
disposing the mixed powder body on the surface of the current
collecting foil which is being conveyed by the roller B. Thus, the
deposition layer in which the active material particles and the
binder particles are deposited and no solvent is included is formed
on the surface of the current collecting foil.
[0005] Thereafter, in a heat pressing process, the
deposition-layer-formed current collecting foil having the
deposition layer on the surface thereof is heated and compressed by
a pair of heat pressing portions of a heat pressing device to form
an electrode layer on the surface of the current collecting foil.
Specifically, the deposition-layer-formed current collecting foil
is made to pass (to be applied with heating-roller pressing)
between a pair of heating rollers (a first heating roller and a
second heating roller) as the pair of the heat press portions, and
thus the deposition layer is compressed in its thickness direction
and the binder particles included in the deposition layer are
softened and molten. By the thus softened and molten binder
particles, the active material particles are bound to one another
and the deposition layer is bound to the surface of the current
collecting foil. As a result of this, the deposition layer becomes
the electrode layer and the electrode layer is formed on the
surface of the current collecting foil.
SUMMARY
Technical Problems
[0006] In the above-mentioned manufacturing method, when the
electrode layer is formed on the surface of the current collecting
foil by heating and compressing the deposition-layer-formed current
collecting foil in the heat pressing process, a surface of the
deposition layer is increased its adhesion due to the softened or
molten binder particles existing on the surface of the electrode
layer (the deposition layer), and thus the surface of the electrode
layer sometimes adheres (sticks) to the heat press portion (the
first heating roller with which the surface of the deposition layer
is contacted). Further, when the surface of the electrode layer is
to be separated from the heat press portion (the first heating
roller with which the surface of the deposition layer is
contacted), a part of the electrode layer could be detached (peeled
off) from the surface of the current collecting foil and adheres
(is transferred) to the heat press portion (the heat press portion
with which the surface of the deposition layer is contacted) of the
heat pressing device. Furthermore, there has been a demand for an
electrode plate achieving improvement in the charge and discharge
characteristics of a battery.
[0007] The present disclosure has been made in view of the above
situation and has a purpose of providing a manufacturing method for
an electrode plate that can reduce the problem that "a part of an
electrode layer is detached (peeled off) from a surface of a
current collecting foil and adheres (is transferred) to a heat
press portion of a heat pressing device," and an electrode plate
achieving improvement in the charge and discharge characteristics
of a battery.
Means of Solving the Problems
[0008] One aspect of the present disclosure is a manufacturing
method for an electrode plate including an electrode layer on a
surface of a current collecting foil, the method comprising:
deposition-layer forming of forming a deposition layer, in which a
plurality of active material particles and a plurality of binder
particles are deposited and no solvent is included, on the surface
of the current collecting foil; and heat pressing of forming the
electrode layer on the surface of the current collecting foil by
heating and compressing a deposition-layer-formed current
collecting foil, in which the deposition layer exists on the
surface of the current collecting foil, by use of a pair of heat
press portions of a heat pressing device, wherein the deposition
layer includes a first deposition layer placed on a side of the
current collecting foil and a second deposition layer constituting
a surface of the deposition layer, the deposition layer is formed
in the deposition-layer forming such that a content rate of the
binder particles in the second deposition layer is lower than the
content rate of the binder particles in the first deposition
layer.
[0009] According to the above-mentioned manufacturing method, in
the deposition-layer forming, the deposition layer, in which the
active material particles and the binder particles are deposited
and no solvent is included, is formed on the surface of the current
collecting foil. The deposition layer includes the first deposition
layer placed on the side of the current collecting foil and the
second deposition layer constituting the surface of the deposition
layer. As the first deposition layer, a layer to be in contact with
the surface of the current collecting foil can be given as an
example. Further, as the second deposition layer, a layer deposited
on a surface of the first deposition layer to form a surface of the
deposition layer can be given as an example.
[0010] Further, in the above-mentioned manufacturing method,
thereafter, in the heat pressing, the deposition-layer-formed
current collecting foil having the deposition layer formed on the
surface of the current collecting foil is heated and compressed by
the pair of the heat press portions of the heat pressing device to
form the electrode layer on the surface of the current collecting
foil. In the heat pressing, the deposition layer is compressed in
its thickness direction and the active material particles are bound
to one another by the softened or molten binder particles so that
the deposition layer is bound to the surface of the current
collecting foil. Accordingly, the deposition layer becomes the
electrode layer, and the electrode layer is formed on the surface
of the current collecting foil.
[0011] Incidentally, in the above-mentioned manufacturing method,
in the deposition layer forming, the deposition layer is formed in
a manner that the content rate of the binder particles in the
second deposition layer (the layer as a part of the deposition
layer constituting the surface of the deposition layer) is lower
than the content rate of the binder particles in the first
deposition layer (the layer as a part of the deposition layer
placed on the side of the current collecting foil). Accordingly, in
the heat pressing, the second deposition layer having relatively
low content rate in the binder particles of the deposition layer is
to be in contact with the heat press portions of the heat pressing
device. Thus, in the heat pressing, the surface of the deposition
layer is hard to adhere (stick) to the heat press portions, and
accordingly it is possible to reduce the problem that "a part of
the electrode layer is detached (peeled off) from the surface of
the current collecting foil and sticks (is transferred) to the heat
press portions of the heat pressing device."
[0012] As the heat pressing device, there is given a heat pressing
device including a pair of heating rollers (a first heating roller
and a second heating roller) configured such that the
deposition-layer-formed current collecting foil is made to pass
between the first heating roller and the second heating roller to
heat and compress (heat roll-pressing) the deposition-layer-formed
current collecting foil, for example. The pair of the heat press
portions of this heat pressing device are the first heating roller
and the second heating roller.
[0013] Further, as the heat pressing device, there is given a heat
pressing device including a pair of heating plates (a first heating
plate and a second heating plate) configured such that the
deposition-layer-formed current collecting foil is held between the
first heating plate and the second heating plate to heat and
compress the deposition-layer-formed current collecting foil, for
example. The pair of the heat press portions of this heat pressing
device are the first heating plate and the second heating plate.
Furthermore, the deposition layer and the electrode layer may
include conductive particles such as acetylene black in addition to
the active material particles and the binder particles.
[0014] Further, in the above-mentioned manufacturing method for the
electrode plate, preferably, the deposition-layer forming includes:
forming the first deposition layer formed of first composite
particles in which the binder particles having smaller diameter
than the active material particles are bound to surfaces of the
active material particles and no solvent is included; forming the
second deposition layer formed of at least any one of the active
material particles and second composite particles in which less
binder particles than those included in the first composite
particles are bound to the surfaces of the active material
particles and no solvent is included.
[0015] In the above-mentioned manufacturing method, in the
deposition-layer forming, there is formed the first deposition
layer formed of the first composite particles, in which the binder
particles having the diameter smaller than the active material
particles are bound to the surfaces of the active material
particles. Further, there is formed the second deposition layer
formed of at least any one of the active material particles (the
active material particles to which no binder particles are bound)
and the second composite particles in which the binder particles
less than those included in the first composite particles are bound
to the surfaces of the active material particles. Therefore, the
number of the binder particles existing around the active material
particles included in the second deposition layer is less than the
number of the binder particles existing around the active material
particles in the first deposition layer.
[0016] Accordingly, in the heat pressing, the second deposition
layer having relatively less number of binder particles around the
active material particles in the deposition layer is to be in
contact with the heat press portions of the heat pressing device.
Thus, in the heat pressing, the active material particles contacted
with the heat press portions are hard to adhere (stick) to the heat
press portions, and accordingly it is possible to reduce the
problem that "a part of the electrode layer is detached (peeled
off) from the surface of the current collecting foil to stick (be
transferred) to the heat press portions of the heat pressing
device."
[0017] Herein, the first composite particles and the second
composite particles are particles in which the binder particles
having the smaller diameters than the active material particles are
bound to the surfaces of the active material particles and no
solvent (liquid) is included. Specifically, the first composite
particles and the second composite particles are particles in which
at least a plurality of the binder particles are bound to the
surfaces of the active material particles, and the composite
particles may be the particles in which conductive particles such
as acetylene black other than the binder particles are bound to the
surfaces of the active material particles.
[0018] Another aspect of the present disclosure is an electrode
plate comprising: a current collecting foil; and an electrode layer
provided with a plurality of active material particles and a
plurality of binder particles and formed on a surface of the
current collecting foil, wherein the electrode layer includes a
first electrode layer placed on a side of the current collecting
foil and a second electrode layer constituting a surface of the
electrode layer, and a content rate of the binder particles in the
second electrode layer is lower than the content rate of the binder
particles in the first electrode layer.
[0019] In the above-mentioned electrode plate, the electrode layer
includes the first electrode layer placed on the side of the
current collecting foil and the second electrode layer constituting
the surface of the electrode layer. As the first electrode layer, a
layer contacted with the surface of the current collecting foil can
be given as an example. Further, as the second electrode layer, a
layer placed (laminated) on the surface of the first electrode
layer to constitute the surface of the electrode layer can be given
as an example.
[0020] Further, in the above-mentioned electrode plate, the content
rate of the binder particles in the electrode layer is less in the
second electrode layer constituting the surface of the electrode
layer than in the first electrode layer placed on the side of the
current collecting foil. Thus, reduction in the content rate of the
binder particles on the surface-side of the electrode layer leads
to improvement in the charge and discharge characteristics in a
battery. For example, when the above-mentioned electrode plate is
used as an electrode plate (a positive electrode plate or a
negative electrode plate) of a lithium-ion secondary battery, there
is less binder particles which obstruct coming in and out
(insertion and detachment) of lithium ions on the surface of the
electrode layer, and thus the lithium ions are easy to come in and
out (insertion and detachment) of the surface of the electrode
layer. Accordingly, the charge and discharge characteristics of the
lithium-ion secondary battery is improved.
[0021] Further, the above-mentioned electrode plate is, preferably,
the electrode layer is formed such that the active material
particles are bound by the binder particles having smaller
diameters than those of the active material particles, and the
number of the binder particles existing around the active material
particles included in the second electrode layer is less than the
number of the binder particles existing around the active material
particles included in the first electrode layer.
[0022] In the above-mentioned electrode layer of the electrode
plate, a plurality of the active material particles are bound to
one another via the binder particles having the smaller diameter
than the active material particles. Then, in this electrode layer,
the number of the binder particles existing around the active
material particles in the second electrode layer (the layer
constituting the surface of the electrode layer) is less than the
number of the binder particles existing around the active material
particles in the first electrode layer (the layer placed on the
side of the current collecting foil).
[0023] In this manner, reduction in the number of the binder
particles around the active material particles on the surface-side
of the electrode layer leads to improvement in the charge and
discharge characteristics of a battery. For example, when the
above-mentioned electrode plate is used as an electrode plate (a
positive electrode plate or a negative electrode plate) of a
lithium-ion secondary battery, there are less binder particles
which obstruct coming in and out (insertion and detachment) of the
lithium ions in the active material particles existing on the
surface of the electrode layer, and thus the lithium ions are easy
to come in and out (insertion and detachment) of the surface of the
electrode layer. Accordingly, the charge and discharge
characteristics of the lithium-ion secondary battery is
improved.
BRIEF DESCRIPTION OF THE DRAWINGS
[0024] FIG. 1 is a schematic sectional view of an electrode plate
in the embodiment;
[0025] FIG. 2 is an enlarged view of a part B in FIG. 1;
[0026] FIG. 3 is an enlarged view of a part C in FIG. 1;
[0027] FIG. 4 is an explanatory view for explaining a manufacturing
method for the electrode plate in the embodiment;
[0028] FIG. 5 is a schematic sectional view of a first composite
particle;
[0029] FIG. 6 is a schematic sectional view of an active material
particle;
[0030] FIG. 7 is another explanatory view for explaining the
manufacturing method for the electrode plate in the embodiment;
[0031] FIG. 8 is another explanatory view for explaining the
manufacturing method for the electrode plate in the embodiment;
and
[0032] FIG. 9 is another explanatory view for explaining the
manufacturing method for the electrode plate in the embodiment.
DETAILED DESCRIPTION OF THE EXEMPLARY EMBODIMENTS
[0033] An embodiment embodying the present disclosure is now
explained in detail below with reference to the accompanying
drawings. The present embodiment applies the present disclosure to
a negative electrode plate for a lithium-ion secondary battery and
manufacturing of the negative electrode plate for the lithium-ion
secondary battery. Specifically, in the present embodiment, the
negative electrode plate for the lithium-ion secondary battery is
exemplified as an electrode plate and a manufacturing method for
the negative electrode plate of the lithium-ion secondary battery
is exemplified as a manufacturing method for an electrode
plate.
[0034] Firstly, a negative electrode plate 100 according to the
embodiment is explained. The negative electrode plate 100 is
provided with a current collecting foil 110 including a first
surface 110b and a second surface 110c and an electrode layer 120
formed on a surface (the first surface 110b) of this current
collecting foil 110 (see FIG. 1). The electrode layer 120 includes
a plurality of active material particles 121 and a plurality of
binder particles 122. This electrode layer 120 includes a first
electrode layer 120A placed on a side of the current collecting
foil 110 and a second electrode layer 120B constituting a surface
125 of the electrode layer 120. The first electrode layer 120A and
the second electrode layer 120B each include a plurality of the
active material particles 121 and a plurality of the binder
particles 122.
[0035] In the present embodiment, the first electrode layer 120A is
a layer contacted with the surface (the first surface 110b) of the
current collecting foil 110 and the second electrode layer 120B is
a layer placed (laminated) on a surface of the first electrode
layer 120A. Further, as the current collecting foil 110, a copper
foil of a thickness of 8 .mu.m is used, and as the active material
particles 121, graphite particles with a grain diameter of 10 .mu.m
are used in the present embodiment. Furthermore, as the binder
particles 122, PVDF particles with a grain diameter of 100 to 200
nm are used.
[0036] In the negative electrode plate 100 of the present
embodiment, a content rate of the binder particles 122 in the
electrode layer 120 is lower in the second electrode layer 120B
constituting the surface 125 of the electrode layer 120 than the
first electrode layer 120A placed on the side of the current
collecting foil 110. In the electrode layer 120, the content rate
of the binder particles 122 on the surface 125 side (the surface
125) is thus made lower, so that the charge and discharge
characteristics can be made preferable in a lithium-ion secondary
battery. Specifically, there are less binder particles 122 which
would obstruct coming in and out (insertion and detachment) of
lithium ions on the surface 125 of the electrode layer 120, and
thus the lithium ions are easy to come in and out (insertion and
detachment) of the surface 125 of the electrode layer 120. As a
result of this, the charge and discharge characteristics of the
lithium-ion secondary battery is improved.
[0037] To be more specific, in the electrode layer 120 of the
negative electrode plate 100 according to the present embodiment, a
plurality of the active material particles 121 are bound to one
another by the binder particles 122 having the smaller diameters
than the active material particles 121. As it is clear by comparing
FIG. 2 and FIG. 3, in this electrode layer 120, the number of the
binder particles 122 existing around the active material particles
121 included in the second electrode layer 120B (the layer
constituting the surface 125 of the electrode layer 120) is less
than the number of the binder particles 122 existing around the
active material particles 121 included in the first electrode layer
120A (the layer placed on the side of the current collecting foil
110). Specifically, the number of the binder particles 122 adhering
to the surfaces of the active material particles 121 in the second
electrode layer 120B is less than the number of the binder
particles 122 adhering to the surfaces of the active material
particles 121 in the first electrode layer 120A (the layer placed
on the side of the current collecting foil 110). Herein, FIG. 2 is
an enlarged view of a part B in FIG. 1 and an enlarged sectional
view of the first electrode layer 120A. Further, FIG. 3 is an
enlarged view of a part C in FIG. 1 and an enlarged sectional view
of the second electrode layer 120B.
[0038] In this manner, the number of the binder particles 122
existing around the active material particles 121 on the surface
125 of the electrode layer 120 is reduced, so that the charge and
discharge characteristics of the lithium-ion secondary battery is
improved. Specifically, there are less binder particles 122 which
obstruct coming in and out (insertion and detachment) of the
lithium ions around the active material particles 121 (the surface
of the active material particles 121) existing on the surface 125
of the electrode layer 120, and accordingly, the lithium ions are
easy to come in and out (insertion and detachment) of the surface
125 of the electrode layer 120. As a result of this, the charge and
discharge characteristics of the lithium-ion secondary battery is
improved.
[0039] Next, a manufacturing method for the negative electrode
plate 100 according to the embodiment is explained. In the
deposition-layer forming process (deposition-layer forming), the
deposition layer 130, in which the active material particles 121
and the binder particles 122 are deposited and no solvent ins
included (see FIG. 8), is formed on the surface (the first surface
110b) of the current collecting foil 110. Specifically, the current
collecting foil 110 made of a copper foil with a thickness of 8
.mu.m is prepared, and as shown in FIG. 4, a resin plate 10, which
is of a thickness of 1 mm and has a through hole 10b of a diameter
of 25 mm, is placed on the first surface 110b of the current
collecting foil 110.
[0040] Subsequently, a plurality of first composite particles 123
are put (fill up) into the through hole 10b of the resin plate 10
to form the first deposition layer 130A formed of a plurality of
the first composite particles 123 on the first surface 110b of the
current collecting foil 110 (see FIG. 4). Herein, the first
composite particle 123 includes no solvent (liquid) and is formed
of a particle in which the binder particles 122 having smaller
diameter than the active material particles 121 are bound to the
surface of the active material particle 121 as shown in FIG. 5. In
the present embodiment, a graphite particle having a particle
diameter of 10 .mu.m (for example, an amorphous carbon coated
graphite particle) is used as the active material particle 121.
Further, PVDF particles each having a diameter of 100 to 200 nm are
used as the binder particles 11. The first composite particles 123
are, for example, obtained by agitating and mixing the active
material particles 121 and the binder particles 122 so that a
plurality of the binder particles 122 are bound to the surfaces of
the respective active material particles 121.
[0041] Subsequently, as shown in FIG. 7, a plurality of the active
material particles 121 (the active material particles 121 to which
no binder particles 122 are bound, see FIG. 6) are dusted over the
surface of the first deposition layer 130A to form the second
deposition layer 130B formed of a plurality of the active material
particles 121 on the surface of the first deposition layer 130A.
Thus, the deposition layer 130, in which the active material
particles 121 and the binder particles 122 are deposited and no
solvent is included, is formed on the surface 110b of the current
collecting foil 110 (see FIG. 7). The deposition layer 130 includes
the first deposition layer 130A placed on the side of the current
collecting foil 110 and the second deposition layer 130B
constituting the surface 135 of the deposition layer 130.
[0042] Herein, in the present embodiment, the first deposition
layer 130A is a layer contacted with the surface (the first surface
110b) of the current collecting foil 110, and the second deposition
layer 130B is a layer deposited on the surface of the first
deposition layer 130A. Further, in the present embodiment, a
thickness of the first deposition layer 130A is set as 1.0 mm, and
a thickness of the second deposition layer 130B is set as 10 to 20
.mu.m. The resin plate 10 is the one to be removed later, and by
removing the resin plate 10, the deposition-layer-formed current
collecting foil 100A having the deposition layer 130 on the first
surface 110b of the current collecting foil 110 is obtained (see
FIG. 8).
[0043] Incidentally, in the present embodiment, the first
deposition layer 130A is formed by a plurality of the first
composite particles 123 (the particles in which the binder
particles 122 are bound to the surface of the respective active
material particles 121), and the second deposition layer 130B is
formed by a plurality of the active material particles 121 (the
active material particles 121 to which no binder particles 122 are
bound) as mentioned above. Accordingly, in the present embodiment,
in the deposition-layer forming process, the deposition layer 130
is formed in a manner that the content rate of the binder particles
122 in the second deposition layer 130B (the layer constituting the
surface 135 of the deposition layer 130) is lower than the content
rate of the binder particles 122 in the first deposition layer 130A
(the layer placed on the side of the current collecting foil
110).
[0044] After that, in the heat pressing process (heat pressing),
the deposition-layer-formed current collecting foil 100A having the
deposition layer 130 on the first surface 110b of the current
collecting foil 110 is heated and compressed in a thickness
direction by a pair of heat press portions (a first heating plate
20 and a second heating plate 30) of a heat pressing device 50 to
form the electrode layer 120 on the first surface 110b of the
current collecting foil 110 (see FIG. 9). In more detail, the first
heating plate 20 is made to be in contact with the surface 135 of
the deposition layer 130 and the second heating plate 30 is made to
be in contact with the second surface 110c of the current
collecting foil 110, and in this state, the deposition-layer-formed
current collecting foil 100A is held between the first heating
plate 20 and the second heating plate 30 to heat and compress the
deposition-layer-formed current collecting foil 100A in the
thickness direction.
[0045] In the present embodiment, each temperature of the first
heating plate 20 and the second heating plate 30 is set as
180.degree. C. The deposition-layer-formed current collecting foil
100A is heated and compressed in the thickness direction by
applying a compression load of 5 tons to the
deposition-layer-formed current collecting foil 100A by these first
heating plate 20 and the second heating plate 30.
[0046] In this heat pressing process, the deposition layer 130 is
compressed in the thickness direction (in an upper and lower
direction in FIG. 9) and the binder particles 122 included in the
deposition layer 130 are softened or molten. By the thus softened
or molten binder particles 122, the active material particles 121
are bound to one another and the deposition layer 130 is bound to
the first surface 110b of the current collecting foil 110. As a
result of this, the deposition layer 130 becomes the electrode
layer 120, and this electrode layer 120 is formed on the first
surface 110b of the current collecting foil 110, and thereby the
negative electrode plate 110 shown in FIG. 1 is manufactured.
[0047] In the manufacturing method of the present embodiment, in
the deposition-layer forming process, the deposition layer 130 is
formed in a manner that the content rate of the binder particles
122 in the second deposition layer 130B (the layer constituting the
surface 135 of the deposition layer 130) is lower than the content
rate of the binder particles 123 in the first deposition layer 130A
(the layer placed on the side of the current collecting foil 110).
Accordingly, in the following heat pressing process, the second
deposition layer 130B of the deposition layer 130, which is
relatively low in the content rate of the binder particles 122, is
to be in contact with the heat press portion (the first heating
plate 20 in the present embodiment). Accordingly, the surface 135
of the deposition layer 130 is hard to adhere (stick) to the heat
press portion (the first heating plate 20) in the heat pressing
process, so that it is possible to reduce the problem that "a part
of the electrode layer 120 is detached (peeled off) from the
surface of the current collecting foil 110 and sticks to the heat
press portion (the first heating plate 20) of the heat pressing
device 50."
[0048] More particularly, in the deposition-layer forming process
of the manufacturing method of the present embodiment, as the first
deposition layer 130A, the one formed of the first composite
particles 123, in which a plurality of the binder particles 122 are
bound to the surface of the active material particle 121, is
formed. Further, as the second deposition layer 130B, the one
formed of a plurality of the active material particles 121 (the
active material particles 121 to which no binder particles 122 are
bound) is formed. Accordingly, the number (the amount) of the
binder particles 122 existing around the active material particles
121 in the second deposition layer 130B is less than the number
(the amount) of the binder particles 122 existing around the active
material particles 121 in the first deposition layer 130A.
[0049] Therefore, in the heat pressing process, the second
deposition layer 130B of the deposition layer 130 including
relatively less number (amount) of the binder particles 122 around
the active material particles 121 is to be in contact with the heat
press portion (the first heating plate 20). Thus, in the heat
pressing process, the active material particles 121 contacted with
the heat press portion (the first heating plate 20) are hard to
adhere (stick) to the heat press portion (the first heating plate
20), so that it is possible to reduce the problem that "a part of
the electrode layer 120 is detached (peeled off) from the surface
of the current collecting foil 110 and sticks to the heat press
portion (the first heating plate 20)."
[0050] The negative electrode plate 100 manufactured as mentioned
above is thereafter combined with a positive electrode plate and a
separator to form an electrode body. Then, after attaching a
terminal member to this electrode body, the electrode body and an
electrolyte are accommodated in a battery case. A lithium-ion
secondary battery is thus completed.
[0051] <Evaluation of Manufacturing Method>
[0052] Four negative electrode plates 100 are manufactured by the
manufacturing method of the above-mentioned embodiment. In any one
of those manufactured negative electrode plates 100, there is
occurred no problem that "a part of the electrode layer 120 is
detached (peeled off) from the surface of the current collecting
foil 110 and sticks (is transferred) to the heat press portion (the
first heating plate 20)."
[0053] On the other hand, other four negative electrode plates are
manufactured by a manufacturing method of a comparative embodiment.
In a deposition-layer forming process of this comparative
embodiment, a deposition layer is formed on a first surface 110b of
a current collecting foil 110 only by first composite particles 123
in which a plurality of binder particles 122 are bound to surfaces
of active material particles 121. In this manner, the deposition
layer is formed such that a content rate of binder particles 122 in
a second deposition layer (a layer constituting a surface of the
deposition layer) is similar to a content rate of the binder
particles 122 in a first deposition layer (the layer placed on a
side of the current collecting foil 110).
[0054] Accordingly, in the comparative embodiment, the content rate
of the binder particles 122 in the second deposition layer
constituting the surface of the deposition layer is higher than
that in the present embodiment. Specifically, in the comparative
embodiment, the number (the amount) of the binder particles 122
existing around the active material particles 121 in the second
deposition layer 130B is larger than that in the present
embodiment. Subsequently, the heat pressing process as similar to
the present embodiment is carried out to manufacture the four
negative electrode plates. When three of the thus manufactured four
negative electrode plates are manufactured, there is occurred the
problem that "a part of the electrode layer 120 is detached (peeled
off) from the surface of the current collecting foil 110 and sticks
(is transferred) to the heat press portion (the first heating plate
20)."
[0055] From the above result, the manufacturing method of the
present embodiment can achieve reduction in the problem that "a
part of the electrode layer 120 is detached (peeled off) from the
surface of the current collecting foil 110 and sticks (is
transferred) to the heat press portion (the first heating plate
20)." The reason for this achievement in the present embodiment is
because, in the deposition-layer forming process, the deposition
layer 130 is formed such that the content rate of the binder
particles 122 in the second deposition layer 130B (the layer
constituting the surface 135 of the deposition layer 130) is lower
than the content rate of the binder particles 122 in the first
deposition layer 130A (the layer placed on the side of the current
collecting foil 110) which is different from the comparative
embodiment.
[0056] Further, the negative electrode plate 100 manufactured by
the manufacturing method of the present embodiment can improve the
charge and discharge characteristics of a lithium-ion secondary
battery as compared with the negative electrode plate manufactured
by the manufacturing method of the comparative embodiment. This is
because the negative electrode plate 100 manufactured by the
manufacturing method of the present embodiment is configured such
that the content rate of the binder particles 122 in the electrode
layer 120 is lower in the second electrode layer 120B constituting
the surface 125 of the electrode layer 120 than in the first
electrode layer 120A placed on the side of the current collecting
foil 110. Accordingly, lithium ions are easy to come in and out
(insertion and detachment) of the surface 125 of the electrode
layer 120, so that the charge and discharge characteristics of the
lithium-ion secondary battery is improved.
[0057] The present disclosure has been explained with the
embodiment as mentioned above, but the present disclosure is not
limited to the above-mentioned embodiment and may naturally be
adapted with appropriate modifications without departing from the
scope of the disclosure.
[0058] For example, in the present embodiment, the manufacturing
method for the negative electrode plate 100 is exemplified as a
manufacturing method for an electrode plate. However, the present
disclosure may be applied to a manufacturing method for a positive
electrode plate not only for the negative electrode plate. When
manufacturing the positive electrode plate, as a first composite
particle, a composite particle in which binder particles and
conductive particles are bound to a surface of an active material
particle is preferably used.
[0059] Further, the present embodiment exemplifies formation of the
electrode layer 120 only on one surface (the first surface 110b) of
the current collecting foil 110, but alternatively, the electrode
layer 120 may be formed on both surfaces (the first surface 110b
and the second surface 110c) of the current collecting foil 110.
Namely, the present disclosure can be applied not only to an
electrode plate having an electrode layer on one surface (a first
surface) of a current collecting foil but also to an electrode
plate having electrode layers on both surfaces (the first surface
and a second surface) of the current collecting foil and to a
manufacturing method thereof. When the electrode layers 120 are to
be formed on both surfaces of the current collecting foil 110, as
mentioned above, the deposition layer 130 is formed on the first
surface 110b of the current collecting foil 110 in the
deposition-layer forming process and a one-side laminated electrode
plate having the electrode layer 120 on the first surface 110b of
the current collecting foil 110 is fabricated by carrying out the
heat pressing process. Thereafter, the deposition layer 130 is
further formed on the second surface 110c of the current collecting
foil 110 of the thus formed one-side laminated electrode plate, and
then the heat pressing process may be carried out.
[0060] Further, in the present embodiment, a strip-shaped current
collecting foil 110 which has been cut into a rectangular shape is
utilized as a current collecting foil, and the leaf-shaped
(strip-shaped) negative electrode plate 100 is fabricated by use of
the heat pressing device 50 including a pair of heating plates (the
first heating plate 20 and the second heating plate 30) as a pair
of heat pressing portions. However, alternatively, the present
disclosure may be applied to a case of manufacturing a long
strip-shaped negative electrode plate by use of a heat pressing
device having a pair of heating rollers (a first heating roller and
a second heating roller) as a pair of the heat press portions by
preparing a long strip-shaped current collecting foil as the
current collecting foil. For example, the deposition layer (the
first deposition layer and the second deposition layer) is formed
on the surface of the current collecting foil while the long
strip-shaped current collecting foil is being conveyed in a
longitudinal direction, and thereafter, the heat pressing process
may be carried out by a pair of the heating rollers.
[0061] Further, in the present embodiment, the second deposition
layer 130B formed of the active material particles 121 is formed as
the second deposition layer. Alternatively, in the present
disclosure, as the second deposition layer, a second deposition
layer may be formed of second composite particles (a plurality of
second composite particles) in which the binder particles 122 less
than those included in the first composite particle 123 are bound
to the surfaces of the active material particles 121. Further
alternatively, the second deposition layer may be formed of a
plurality of the active material particles 121 and a plurality of
the second composite particles.
REFERENCE SIGNS LIST
[0062] 20 First heating plate (heat press portion) [0063] 30 Second
heating plate (heat press portion) [0064] 50 Heat pressing device
[0065] 100 Negative electrode plate (electrode plate) [0066] 100A
Deposition-layer-formed current collecting foil [0067] 110 Current
collecting foil [0068] 110b First surface (surface) [0069] 120
Electrode layer [0070] 120A First electrode layer [0071] 120B
Second electrode layer [0072] 125 Surface [0073] 121 Active
material particle [0074] 122 Binder particle [0075] 123 First
composite particle [0076] 130 Deposition layer [0077] 130A First
deposition layer [0078] 130B Second deposition layer
* * * * *